The present invention relates to coating flexible materials or supports such as sheets of paper or other polymeric material, either woven or non-woven, with a silicone composition. The present invention also relates to the coating of flexible materials or supports with liquid compositions comprising one or more cross-linkable polyorganosiloxanes wherein such polyorganosiloxanes are cross-linkable by an addition reaction, a condensation reaction, a cationic reaction, or a free-radical reaction. The present invention also relates to star branched polyorganosiloxanes (silicone polymers) that reduce misting during the application of the silicone composition (polyorganosiloxane) to the flexible material or support. The flexible support may be paper, cardboard, plastic film, metal film and the like. Some exemplary applications are paper for foodstuffs, adhesive labels, adhesive tapes, seals and the like.
The coating of flexible supports with liquid silicones is typically carried out on coating devices that operate continuously at very high speed. These devices usually comprise coating heads composed of several rolls, including in particular a pressure roll and a coating roll that are continuously fed with a silicone composition that may or may not be cross-linkable, by means of a series of rolls that are placed next to one another. A strip of flexible support of the desired material to be coated is fed at high speed between the pressure roll and the coating roll to be coated on at least one of its surfaces. When it is intended to cross link the silicone coating, apparatus to implement a cross linking reaction are positioned downstream of the coating head. The apparatus that implements cross linking may be for example an oven or an emitter of radiation, e.g. ultraviolet (UV) radiation or an emitter of a beam of electrons (EB).
High speed coating of flexible supports with silicones has been associated with problems associated with the transfer of the silicone liquid (or fluid) from the coating roll to the flexible support, which moves forward through the coating apparatus. One of the particular problems associated with transfer of the silicone liquid from the coating roll to the flexible support is the appearance of a fog, mist or aerosol in the immediate vicinity of the coating head and particularly close to the points of contact between the coating roll and the flexible support being coated. Typically, the density of this fog, mist or aerosol increases with an increase in the forward speed of the flexible support being coated by the apparatus.
The first effect of this transfer problem is to reduce the amount of silicone liquid actually transferred to the flexible support. A second effect is for the droplets comprising the fog, mist or aerosol to condense onto the newly coated flexible support downstream of the coating rolls creating an orange peel effect. This orange peel effect, or coating non-uniformity, creates problems with coverage, the mechanical properties of the coating, e.g. ruboff, and adhesion resistance.
An additional problem caused by non-uniformity in the coating is related to industrial hygiene and the safety of people operating the coating equipment who are working in the vicinity of the coating equipment.
The present invention provides for a composition to reduce misting during the coating of flexible supports comprising the hydrosilylation reaction product of:
a) MaMHbDcDHdTeTHf; and
b) an amount xcex1 of CH2xe2x95x90CHR1 
where xcex1+1xe2x89xa6b+d+f and gxe2x89xa6b, hxe2x89xa6d, ixe2x89xa6f with 1.5xe2x89xa6b+d+fxe2x89xa6100;
2xe2x89xa6a+bxe2x89xa612; 0xe2x89xa6c+dxe2x89xa61000; 0xe2x89xa6e+fxe2x89xa610 and R1 is a monovalent radical selected from the group consisting of halogens, hydrogen, C1 to C60 monovalent hydrocarbon radicals, C1 to C60 monovalent polyester radicals, C1 to C60 monovalent nitrile radicals, C1 to C60 monovalent alkyl halide radicals and C1 to C60 monovalent polyether radicals and mixtures thereof; where
M=R2R3R4SiO1/2;
MH=HR5R6SiO1/2;
D=R7R8SiO2/2;
DH=HR9SiO2/2;
T=R11SiO3/2;
TH=HSiO3/2;
and said reaction product has the formula:
Mxe2x80x2=(CH2CH2R1)R5R6SiO1/2;
xe2x80x83Dxe2x80x2=(CH2CH2R1)R9SiO2/2; and
Txe2x80x2=(CH2CH2R1)SiO3/2
with each R2, R3, R4, R5, R6, R7, R8, R9 and R11 independently selected from the group of C1 to C60 monovalent hydrocarbon radicals where the subscripts a, b, c, d, e, f, g, h, and i are zero or positive subject to the limitations that b+d+fxe2x88x92gxe2x88x92hxe2x88x92i greater than 0.
The present invention further provides for a composition to reduce misting during the coating of flexible supports comprising the hydrosilylation reaction product of:
a) Mgxe2x80x2MaMHbxe2x88x92gDcDhxe2x80x2DHdxe2x88x92hTeTixe2x80x2THfxe2x88x92i and
b) (MjMVikDlDVimTnTVio)pQp)q where
the subscripts j, k, l, m, n, o and p are zero or positive subject to the limitation that k+m+o greater than 0, k+m+o less than b+d+fxe2x88x92gxe2x88x92hxe2x88x92i, p ranges from 0.4 to 4.0, q is non-zero and positive subject to the limitation that:
(b+d+fxe2x88x92gxe2x88x92hxe2x88x92i)/(((k+m+o)p)q) ranges from 4.59 to 0.25, where
MVi=RViR5R6SiO1/2;
DVi=RViR10SiO2/2;
TViRViSiO3/2;
Q=SiO4/2; where
R10 is independently selected from the group of C1 to C60 monovalent hydrocarbon radicals and each RVi is independently selected from the group of C2 to C60 monovalent alkenyl hydrocarbon radicals.